Simple design to make solar water heating affordable and compatible with conventional water heaters

ABSTRACT

The objective of this invention is to make solar water heating affordable and compatible with conventional gas or electric water heaters. Solar energy is clean and renewable. However, solar water heating has not been in wide use in the US mainly due to two reasons: first, the cost of a current solar water heater is generally too expensive for an average household; second, a typical solar water heater uses ethylene glycerol as a heat transfer fluid to prevent freezing and needs additional space for an extra exchange tank. Our design includes evacuated tube collector panels for efficient collection of solar energy, utilizes two unique three-way adaptors to connect solar collector panels to a conventional water heater for storing solar hot water, and is operational even in freezing temperature. These improvements eliminate the need for an extra exchange tank and significantly reduce the cost of a solar water heater.

Solar water heating is an efficient way to utilize energy from the Sun and is beneficial to the environment. However, solar water heating is not in wide use in the US because commercially available systems of solar water heating are too complicated and too expensive for ordinary people. The present invention relates to a simple design to make solar water heating affordable and compatible with conventional gas or electric water heaters.

This device is comprised of the following components:

-   -   A. Evacuated solar collector panels (collect solar energy to         heat water passing through the collector panels)     -   B. Temperature sensors (detect the temperature at a certain         location within the system).     -   C. Controller (receives information from the temperature sensors         and decides whether to turn on/off the circulation pump).     -   D. Circulation pump (circulates water within the system).     -   E. Three-way adaptors (connect solar collector panels to the         conventional water heater and the drain).     -   F. Expansion tank (relieves water pressure within the system).     -   G. Pressure/temperature relief valves (reduce high water         pressure or temperature due to over-heating within the system).     -   H. Check valves (prevent back flow of water within the system).

After successful assembly and connection to the conventional water heater, these components work together in the following ways:

-   -   A. Turn the temperature setting on the existing gas or electric         water heater to vacation or warm (This will depend on how much         solar energy is available at a given location).     -   B. When the temperature at Sensor T1 (1 a) near the solar         collector panels is higher than temperature at Sensor T2 (1 b)         near the tank by a pre-set value (usually 20° C.) during the         day, the Controller (2) will activate the Pump (3) to circulate         hot water from the solar collector panels into the conventional         water heater. Direction of the water flow is indicated by arrows         in FIG. 1.     -   C. Once the temperature differential between Sensor T1 and         Sensor T2 decreases to below a pre-set value (usually 10° C.),         the Controller (2) will turn off the pump (3).     -   D. When hot water is drawn from the water heater at night, cold         water flows into the tank as indicated by arrows in FIG. 2.     -   E. In the winter, outside temperature may fall below freezing at         night.     -   When the pipeline temperature is below a pre-set point (usually         2° C.) near the collector panels at Sensor T3 (1 c), the         Controller (2) will activate the Pump (3) to re-circulate hot         water collected during the day. Once the temperature reaches         another pre-set value (usually 8° C.) at Sensor T3, the         Controller (2) will turn off the Pump (3). Since the pipelines         are well insulated within the system, minimal amount of         circulation is able to prevent freezing.     -   F. Power supply to the system can be backed up by a battery bank         equipped with an inverter to convert direct current to 110 volt         alternating current in case of a power grid failure.     -   G. In extremely cold and cloudy winter when it is not sufficient         for solar collector panels to heat the water, connection to the         solar collector panels can also be cut off. This is done by         un-plugging the power to the Controller (2), turning off the         Ball Valves (4), and draining the system through the Sillcock         Valves (5) as shown in FIG. 3.     -   H. The Expansion Tank (6) and the Pressure/temperature Relief         Valve (7) are installed as precaution measures to protect the         system from extreme water pressure and temperature due to         over-heating.     -   I. The Check Valves (8) prevent hot water in the conventional         water heater from escaping towards the solar collector panels in         cold weather or at night.

The design may be used for solar heating of swimming pools and other sources of hot water with minimal modifications.

The design may not need all three temperature sensors in locations where freezing never occurs. The evacuated solar collector panels are modular in nature, two or more panels can be connected in tandem to increase the amount of solar energy collection.

DRAWING DESCRIPTIONS

FIG. 1 is a schematic diagram of the invention for collecting solar hot water during the day.

FIG. 2 is a schematic diagram of the invention for using solar hot water at night.

FIG. 3 is a diagram of the unique three-way adaptor. 

What is claimed is:
 1. The way this invention works is that the design includes evacuated tube collector panels for efficient collection of solar energy, utilizes conventional gas or electric water heater as the tank for storing hot water directly from the solar collector panels. When there is enough sunlight, hot water will be provided solely by the solar collector panels and stored in the conventional water heater. When there is not enough sunlight, water heating can also be supplemented by gas or electric heating in the conventional water heater.
 2. Unique three-way adaptors that connect the solar collector panels to the conventional water heater through Ball valves and to the drain through Sillcock valves. 